Wednesday, September 5, 2012

Meet the New Faculty: Jacob Rosenstein

Biological sensors that detect currents at the nanoscale would have important clinical applications, but how to separate signal from noise when the current lasts for 10 microseconds? Jacob Rosenstein has theories and devices that enable measurement at small timescales.

Jacob Rosenstein enjoyed his undergraduate years at Brown and certainly made the most of them. He graduated magna cum laude and co-founded a company with Anubhav Tripathi, associate professor of engineering. Still, when Rosenstein graduated in 2005, continuing in academia was far from his mind.

But seven years later, following a stint in the semiconductor industry and now all but finished with a Ph.D. from Columbia University, he’s set to return to Brown for a job as an assistant professor of engineering. Much as he did while a Brown student, he plans to continue innovating at the nexus of electronics and biology.

“Integrated circuits are all around us, but historically most of the industry focus has been toward computing and communications,” says Rosenstein. “I’m excited to see what we can do to leverage all of that advanced technology for biological and chemical sensors.”

Rosenstein was a busy senior at Brown. At the same time he was developing a new microphone array platform with Harvey Silverman, professor of engineering, he was also working with Tripathi to develop instruments for microfluidic chips, which are integrated circuits that control the flow of fluids rather than electrical current. They founded Gauge Microfluidics in Providence to commercialize the work.

With a resumé of academic brilliance and entrepreneurship, it didn’t take long for Rosenstein to find an industry job. Shortly after graduation, he moved to Boston to join Analog Devices, a major player in the semiconductor business. He worked in the company’s wireless division, helping to develop and test application-specific integrated circuits and working on prototype cell phone designs.

Rosenstein worked at Analog for more than two years before his whole business unit was sold to the Taiwanese company MediaTek. He was still happy there, but he had begun to do some professional soul searching. The desire to gain more experience in chip design led him back to the notion of graduate school. He enrolled at Columbia in 2008.

In the Bioelectronic Systems Lab of Kenneth Shepard at Columbia, Rosenstein returned to the practice of bringing silicon technology to bear on biophysical systems. At Columbia, his main project has been the design of an integrated circuit amplifier to improve measurements of weak ionic currents. Cell membranes contain a variety of proteins which regulate the movement of dissolved ions in and out of the cell, and the movement of these ions can be measured as an electrical current. However, in many cases this current is very small, making it difficult to measure the signal above the noise. Rosenstein’s amplifier reduces the noise level at high frequencies, considerably improving the quality of fast ion channel recordings.

“As you get down to the range of 10 microseconds or less it gets very difficult to measure that weak current,” he said. “Where I’ve come in is to make new electronics and experimental setups to reduce the noise level and therefore enable measurements at timescales that people have not been able to measure.”

Researchers have been also able to make biosensors inspired by ion channels using very tiny holes called “nanopores.” If its diameter is not much larger than a single molecule, a nanopore can yield a change in its ionic current when a molecule such as DNA passes through the pore. However, these weak signals are usually very brief, making them difficult to measure. In a paper earlier this year in Nature Methods, Rosenstein demonstrated that signals as fast as 1 microsecond can be recorded from individual DNA molecules when a nanopore is integrated with his custom amplifier.

Now back at Brown, Rosenstein is looking forward to exploring other opportunities in bioelectronics. He said the University’s success in harnessing signals directly from neurons in the brain with the BrainGate sensor is a particularly inspiring example.

“There are a lot of other interesting diagnostics, sensors, and hybrid systems that are mostly unexplored,” he said. “I’m very excited to test the waters and get to know the pure sciences and life sciences groups at Brown, and hopefully I can be a hub of instrumentation, sensing, and high-performance electronics.”